The invention relates to an adjustable attenuation equalizer in the circuit of a four-terminal network for the correction of the frequency-related attenuation characteristic of cables, said equalizer being composed of a bridged T circuit containing ohmic resistances and having two ohmic series resistances, preferably of the same resistance value, bridged by a bridging impedance. The bridging impedance consists of a series-resonant circuit containing an inductance, a condenser and a variable resistance in parallel, while the shunt impedance is formed of a parallel-resonant circuit containing an inductance, a condenser, and a variable series resistance. Both variable resistances are adjusted by a common mechanical traversing means.
The starting point of this invention is Australian Patent Application A 9530/73, in which the problem of finding an equalizer which will equalize the attenuation curve of transmission lines and circuits by means of a simple-to-operate circuit having optimum input and output matching was solved by purely electrical means. The present invention provides a structural component by which the equalization of the attenuation, especially in the case of relatively long conductors, and particularly in broad-band cable connections for telephone installations, cable television, community antenna installations or the like, will be accomplished in accordance with the known electrical circuit, taking into account especially the peculiarities of the ultra-high frequency range up to approximately 900 MHz.